(1) Field of the Invention
The present invention relates to biometric authentication technology that authenticates individuals by using their biometric features.
(2) Description of the Related Art
A user authentication system that uses biometric data captures biometric data from a user during enrollment, and extracts and enrolls information called features. The enrollment information is referred to as a template. During authentication, the system captures biometric data from the user again to extract features, and matches it with the template to determine whether the user is a principal. When an authentication server authenticates the user at a client side based on biometric data via a network, it generally holds the template. The client captures user's biometric data during authentication to extract features, and transmits them to the authentication server. The authentication server matches the features with the template to determine whether the user is a principal.
Advantageously, biometric authentication is difficult to forge and never fails to be forgotten. However, disadvantageously, since it is said that biometric data such as fingerprints and irises is unchanged for life, and the number of pieces of biometric data of one user is limited (for example, the number of fingerprints is only 10), if templates enrolled in the authentication server leak and a fear of personating occurs, enrollment information cannot be easily discarded or updated, so that safety cannot be restored.
For this problem, U.S. Pat. No. 6,836,554 discloses biometric data concealment-type authentication that converts features by a certain type of a conversion function, and performs enrollment and matching in a concealed state. In the biometric data concealment-type biometric authentication system, since an authentication server performs authentication without knowing features, even if templates and matching information leak from the authentication server, the original features and biometric data are not revealed, contributing to preventing a threat of being used to create forged living body.
The biometric data concealment-type authentication system cannot prevent a threat of personating when templates enrolled in a server and matching information used when legal users are authenticated leak. Since the templates are information that is managed within the server and is not transmitted to the outside, a leak risk can be reduced by operation. However, since the matching information used when legal users are authenticated is information transmitted from a client to a server, a leak risk is high.